Adding bookmark functionality is relatively easy and it enables our ADO recordset to be used with a greater number of data bound controls.
IRowsetLocate and bookmarks
To support some of the more demanding data bound controls we need to support bookmarks. The proxy rowset that we developed in the last article already has some support for bookmarks built in, but the rowset itself doesn’t expose IRowsetLocate, or the bookmark related properties, so the bookmark functionality can’t be used by consumers.
The ATL OLE DB Provider templates appear to rely on the fact that your data is kept in a simple array, but that’s not really the case at all!
Implementing a custom OLE DB rowset
This article continues from where we left off in the previous article. We have all of the framework in place to provide ADO recordset interfaces on our simple data object. All we need to do now is replace the wizard-generated OLE DB rowset object with one that allows us to access our object’s data.
ADO seems to be the ideal way to expose tabular data from your own COM objects and the ATL OLE DB Provider templates can help!
The problem
If you already have a COM object that manages data that is naturally tabular, or, if you have a COM object that has data which is often displayed in a tabular form then it would seem sensible to leverage the work being put into ADO by third party data control manufacturers.
Templates are a great way of reusing code, unfortunately MFC makes it hard to write MFC friendly template classes…
The problem… Templates are cool. Being able to write code that can work on objects of any type that satisfies the minimum functionality that you require make reusing code considerably easier. No more type-unsafe generic coding methods, like void *’s and macros. Templates solve all manner of problems.
Using templates with MFC classes, especially MFC classes with message maps isn’t easy.
COM objects generally provide access to sequences using an IEnumXXXX style interface, this class wraps that with an STL style iterator
The problem Many COM interfaces provide the ability to step through, or enumerate, a collection of some kind. The usual way for a COM interface to expose this kind of functionality is via an interface which conforms to the IEnumXXXX standard.
IEnum interfaces provide the following methods: Next(), Skip(), Reset() and Clone().
In February 1995 I flew to Perm in eastern Russia as part of a two-man team installing a smartcard system for a local bank. I was responsible for designing and implementing the card production system that was being used.
For a marketing view of the system that we installed, visit Interlink’s Smart Bank pages. For a personal view, stay tuned…
The other member of the team, David Steed, worked on the overall design and the integration of the system into Interlink’s standard transaction processing system.
John Fernberg. RPA Elite, SAMAS 261.
I’d wanted to be “Sam” ever since my fifth birthday. It was Freedom Day and the local garrison had staged a fly by as part of the celebrations. I can remember the smell of pop-corn and fresh muffins, sitting on Dad’s shoulder so I could see. The whole town had turned out and there was a crowd bigger than I’d ever seen. I sat on a rock in a sea of heads.
The Order of the Silver Rose was a religious order of Knights in an AD&D campaign that I ran. The campaign was set in The Forgotten Realms and was based around the FRE1-3 scenario packs.
The Order of the Silver Rose
The order of the Silver Rose is a religious order of Knights devoted to worship of the demigod Torm. The order was formed around thirty years ago by Sir Giriath of Iriaebor a dedicated Knight of Torm who, single-handed, slew the Great Dragon, Dyldarin the Red.
